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Abstract:
It has been suggested that nouns and verbs are processed by
topographically distinct cortical cell assemblies. For example,
nouns, as functionally related to perceptual entities, should be
closely tied to sensory areas while verbs, denoting motor acts,
should be tied to motor areas. To objectify such differences we
studied the N400 effect for German verbs and nouns in a minimal
sentence context. Nouns were primed by a predicate and a subject
(e.g. ,Holz" was primed by ,saegen - Tischler" ), while verbs were
primed by their fitting subject and object (e.g. ,saegen" was
primed by ,Tischler - Holz"). Participants had to silently generate
a best matching third word after the primes. After a short delay a
target (noun or verb) was presented whose relatedness to the
generated word had to be judged. Relatedness between primes and
best matching target was varied in four levels. Event-related
potentials (from 124 scalp positions referenced to nosetip) and
reaction times were measured. RTs were systematically affected by
the relatedness between primes and target and by the target word
category. Correspondingly, an increase of the negative amplitude
within the N400 latency window was observed with decreasing
relatedness ratings. The standardized topography between 540 and
720 ms revealed a topographic difference of the N400 effect for
nouns and verbs, with a more fronto-parietal maximum for
verbs.
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